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Viewing 1 to 30 of 56
Technical Paper
2014-04-01
Guangqiang Wu, Shuyi Jin
During a car launch, the driving torque from driveline acts on brake disk, and may lead the pad to slip against the disk. Especially with slow brake pedal release, there is still brake torque applies on the disk, which will retard the rotation of disk, and under certain conditions, the disk and pad may stick again, so the reciprocated stick and slip can induce the noise and vibration, which can be transmitted to a passenger by both tactile and aural paths, this phenomenon is defined as brake groan. In this paper, we propose a nonlinear dynamics model of brake for bidirectional, and with 7 Degrees of Freedom (DOFs), and phase locus and Lyapunov Second Method are utilized to study the mechanism of groan. Time-frequency analysis method then is adopted to analyze the simulation results, meanwhile a test car is operated under corresponding conditions, and the test signals are sampled and then processed to acquire the features. Finally, the results of the simulation and those of the test are compared, and the mechanism of groan and its contributory factors are revealed.
Technical Paper
2014-04-01
Yoon Cheol Kim, Seong Jin Kim, Jaeyoung Lee, Jeongkyu Kim, SooHyuk Lee, Kyoungdon Yi, KiJeong Kim
Abstract Reducing unsprung mass of the car is a representative method to enhance the ride & handling performance and fuel efficiency. In this study, brake disc weight is reduced 15∼20% using a hybrid type material. The basis for this study is the separation of the friction surface and HAT(mounting part). Aluminum material is applied in the HAT for a light weight effect. Gray iron is applied in the friction surface section to maintain braking performance. Two types of joining between aluminum and cast iron are developed. One is the aluminum casting method utilizing a gray iron insert and the other is a bolted assembly method. Detailed structure, process and material are optimized using try-out & dynamometer experiments. The Reliability of this development is proved through durability (dynamometer and vehicle) testing.
Technical Paper
2013-09-30
Toshikazu Okamura
The surface texture of a brake disc in some cases affects the braking effectiveness of a vehicle in the early stages of use. Brake discs usually turn in one rotational direction during their finishing process but are turn in two directions on a vehicle. This causes a difference in friction or wear between two wheels. Directional surface textures of brake discs finished by turning or roller burnishing may cause this interaction to become more severe than those finished by grinding. Full-scale tests using actual friction pairs are effective for estimating the total braking performance of a full vehicle or its corners. However, they are exposed to various factors and different brake-disc locations creating different friction and wear histories. The author, therefore, concluded that fundamental experiments using small-scale specimens are necessary to examine the details of the interaction between the disc surface texture, rotational direction, and friction material. In this paper, the author reports the results of the first series of experiments, which consisted of thirty disc surface textures and a friction material under an on-brake-drag condition.
Technical Paper
2013-09-30
SeongJoo Lee, ShinWook Kim, ShinWan Kim, SeongKwan Rhee
Two sets of OE quality brake discs were evaluated for their equivalence in friction and wear under a humidity controlled condition in order to avoid the influence of humidity on friction and wear. These discs were received from two different suppliers located in two different countries. Small differences were found in disc chemistry and microstructure, which resulted in differences in disc properties, and friction and wear characteristics. It is recommended that extreme care must be exercised in determining the performance equivalence of one disc from one supplier against another disc from a second supplier.
Technical Paper
2013-09-30
David B. Antanaitis
Driving on the race track is an especially grueling situation for the automotive brake system. Temperatures can exceed the phase transition temperature of the disc material, wear rates of friction material can be orders of magnitude higher than during street use, and hydraulic pressures and mechanical stresses on components can approach their design limits. It is a given that friction material under these conditions will wear unevenly - causing taper and cupping wear - and an associated set of performance degradations will occur, including an increase in fluid consumption (pedal travel increase) and loss of mechanical efficiency (pedal force increase). Some high performance vehicles use surface features on brake discs, such as crossdrilling or slotting, to improve apparent friction levels in aggressive use (as well as to add marketing appeal), and generally accept a significant degradation in lining wear characteristics (both in overall wear rates and in the exacerbation of uneven wear behaviors) in order to achieve this.
Technical Paper
2013-07-15
Ali Belhocine, Mostefa Bouchetara
The main purpose of this study is to analyze the thermomechanical behavior of the dry contact between the brake disc and pads during the braking phase. The simulation strategy is based on computer code ANSYS11. The modeling of transient temperature in the disc is actually used to identify the factor of geometric design of the disc to install the ventilation system in vehicles. The thermal-structural analysis is then used with coupling to determine the deformation and the Von Mises stress established in the disk, the contact pressure distribution in pads. The results are satisfactory when compared to those of the specialized literature.
Technical Paper
2012-09-17
Young Min Kim, Ju Young Kim, Jeongkyu Kim
In order to reduce brake squeal noise, it is important to identify operational deflection shape (ODS) of brake disc while squeal arises. However, in the conventional modal analysis and optical measurement, it is only able to identify limited ODS because of the technical limits. This paper details the test method to identify ODS in radial and tangential as well as axial direction of a brake disc in driving condition. Vibrational signal of a rotating disc was obtained by triaxial accelerometer installed to solid type discs/cooling fins of ventilated type discs, then ODS of disc were analyzed through digital signal processing.
Technical Paper
2012-09-17
Gabriel Hurel, Jean-Frédéric Diebold lng, Sébastien Besset, Louis Jézéquel
Aeronautical brakes are subject to non-linear unstable vibrations. In particular, two modes appear and present a risk for the structure. Firstly, the whirl modes consist of a rotating bending motion of the axle out-of-phase with the brake torque tube. It is due to a coupling of two bending modes of the axle in orthogonal directions. Secondly, the brake squeal mode resulting from stick-slip or sprag-slip phenomena consists of a rotational motion of the brake around the axle. Those vibrations are not resulting from an external excitation but are friction-induced self-excited. Hence, they are dependent on tribological phenomena specific to carbon disks and are in particular controlled by the friction coefficient μ. In order to take into account the dynamical aspect in brake design, Messier-Bugatti-Dowty wants to simulate modes and acceleration g's levels. This article deals with the improvement of such a model. A finite element of the brake exists. It is able to reproduce whirl modes and squeal mode.
Technical Paper
2012-09-17
Anish Poudel, Tsuchin Chu, Peter Filip
This paper discusses the application of an air-coupled ultrasonic non-destructive evaluation (NDE) method for aircraft braking materials. The main objective of this research work was to identify and characterize flaws such as delaminations, cracks, porosity (resin pockets), and disbonds in commercial Carbon/Carbon (C/C) composite aircraft brake disks. Air-coupled ultrasonic testing (ACUT) method was applied for the inspection of commercial C/C brake disks. Several tests were performed by using various air-coupled ultrasonic transducers at center frequencies 50, 120, 125, 225, 400, and 436 kHz in a through-transmission mode by varying scan increments and resolutions. It was found that a testing frequency of 125 kHz provided the best results for commercial C/C composite aircraft brake disks. The relative through-transmitted ultrasonic signal drop in the defect areas was around −18 dB which allowed for easy distinction of abnormal regions within the C/C brake disks. In addition, material inhomogeneity within the C/C brake disks was also revealed by the ACUT C-scan results.
Technical Paper
2012-09-17
Fabrizio Merlo, Umberto Passarelli, Diego Pellerej, Pietro Buonfico
Brake pad material formulation and disc microstructure/composition plays a mutual role during wear test due to the third body layer (TBL) formation and its relative evolution due to temperature change. Nevertheless these ones could influence corrosion behavior. In this study we investigated the effect of rotors characteristics on wear and sticking behavior. Rotor and brake pad microstructure were analysed with optical, metallographic and scanning electron microscope to understand the surface and TBL evolution (using different thermal preconditioning) taking into consideration also the copper role during the different wear stages. During this preliminary study we were able to find out different copper smear morphologies depending on test conditions and rotors features.
Technical Paper
2012-09-17
Arthur L. Swarbrick, Houzheng Wu
Previous research has highlighted that the formation of a sustained friction film, desired for stable and predictable friction performance, is highly dependent upon the region of the substrate (CMC) being examined. In attempt to improve the friction performance, notably bedding-in, research at LU has been developing coatings aimed at ensuring friction film development across the substrate. This paper focuses on the performance of one of these coating formulations, and examines the performance of this on a laboratory scale dynamometer. Subsequently, the coating has then been applied to a full size brake disc, as used on a prestige vehicle, for dynamometer testing at an industry scale for comparative purposes. On both lab and full scale samples the bedding performance shows improvements over the standard material, and at the full scale the coating indicates improved stability of subsequent friction performance through a modified AK Master test schedule. Post-test OM and SEM characterization of the friction surfaces shows that friction film formation has improved over the standard samples, and EDS elemental analysis indicates the presence of the original coating remaining within the formed friction film.
Technical Paper
2012-09-17
Toshikazu Okamura, Hiroyuki Yumoto, Masanori Imasaki
The propensity of brake squeal depends significantly on the vibrational characteristics of disc rotors. In this study, we focused on the differential effects of disc dimensions on the natural frequencies of various vibration modes. We analyzed the results of the CAE factorial experiments presented in our previous paper, which were conducted on four disc rotors with different designs such as front-and back-vented and solid discs. As a result, the effects of disc dimensions on natural frequencies were confirmed to depend on vibration modes, their orders (or the number of nodal diameters), and the basic design of disc rotors. The dimensions that change the stiffness of the friction ring such as ventilation-path width and fin thickness had larger effects on the out-of-plane circumferential modes of high orders than those of low orders. The dimensions around the necking, on the other hand, had a large effect on the low-order modes. The significance of these effects depends on the basic design of disc rotors as well.
Technical Paper
2011-09-18
Toshikazu Okamura
This paper focuses on the interaction in friction behavior between the surface texture of brake discs, rotational directions in braking operations and metal-cutting process, and friction materials with different degrees of aggressiveness. A factorial experiment for front brake discs was conducted by combining eight discs with directional surface finishes, two rotational directions, and two NAO friction materials on a brake dynamometer. The author analyzed several test results, such as the friction coefficients, disc wear, roughness, and the correlation between them. An assumed mechanism describing the friction behavior is discussed using the experimental results and by introducing the contribution of the aggressiveness and adhesiveness to the friction and confirmed by the test results.
Technical Paper
2011-09-18
Vincent Magnier, Jean-Francois Brunel, Martin Duboc, Philippe Dufrenoy
Brake squeal noise has been under investigation by automotive manufacturers for decades due to consistent customer complaints and high warranty costs. Sound in a squealing brake is excited by the contact between pads and the disc. It is well known that the material friction pad consists of several components making it a heterogeneous material. It is also well known that a part of the wear particles agglomerate at the surface leading to non uniform contact properties. The aim of this paper is to investigate the effect of heterogeneities of the friction material on the dynamic behavior of the brake. For this, an analytical model with three degrees of freedom (a translation and a rotation for the pad and a translation for the disc) has been developed including friction at the disc-pad surface contact surface. This model is computed with a complex modal analysis determining the frequencies of the system which can be coalesced to lead to mode lock-in which may be associated to squeal occurrence.
Technical Paper
2011-09-18
Jürgen Lange, Georg Ostermeyer
Metal pickup is a phenomenon that can be observed during dynamic braking with automotive disc brakes. Hard metallic particle agglomerations embedded in the friction materials rubbing surface can lead to severe disc scoring, accelerated wear and deterioration of the friction surface of either brake disc or brake pad. Such kind of surface conditions are also suspected for generating brake squeal, even if a direct root cause effect had not been proven so far. Disc scoring effects have been reported for all kinds of applications, reaching from small passenger cars up to commercial vehicles as well as railroad brakes. Although such phenomena are known since long, they still appear causing problems in brake systems of today. Some recent papers have described the effect and mentioned preferable conditions for the appearance of metal pickup. Specific procedures have been proposed for provocation of the effect to allow a better and more systematic investigation of the influencing parameters. Observations on results of such experiments were described and several working hypotheses put forward with influences going back to the brake rotors metallurgy and surface finish as well as to the friction materials ingredients.
Technical Paper
2009-10-11
Toshikazu Okamura, Masanori Imasaki
Reducing vehicle weight for promoting a sustainable global environment is one of the most significant challenges in the automotive industry. It is difficult to replace cast iron with lighter brake-disc material for ordinary vehicles. Material homogeneity also affects the thermal strength of brake discs. In our previous study, we established an integrated system for developing and manufacturing homogeneous brake discs to reduce judder. With our system, we maintained the thermal strength of a lightweight brake disc by improving its material homogeneity. As a result, we can optimize the brake disc design for reducing a disc's weight and contribute toward sustaining our global future.
Technical Paper
2009-10-11
Kiyotaka Obunai, Kazuya Okubo, Toru Fujii, Tsuyoshi Nakatsuji
The purpose of this study is to characterize the brake torque variation (BTV) of the developed brake system using wave type brake disc. The brake torque was fluctuated when the pad passed at the point of the wavy shape. The indentation of the pad into the space of wavy shape was observed. These results indicate that remarkable peak of the BTV of the wave type brake disc was related with the pad deformation. In the devised test, remarkable peak of the BTV of the wave type brake disc was decreased by insertion of spacers. This paper proposed an effective aspect to prevent the BTV of the wave type brake disc.
Technical Paper
2009-10-11
Jae Young Lee, Hyun Dal Park, Seong Jin Kim, Jae Min Han, Yoon Cheol Kim, Jong Dae Lim, Jeong Kyu Kim
Many engineers have been working to reduce brake noise in many ways for a long time. So far, a progress has been made in preventing and predicting brake noise. Nevertheless, there are some discrepancies of brake noise generation propensity between testing for the prototype and the production. As known in general, the reason for this unpredicted brake noise occurrence in production is partly due to the variation of the resonant frequency, material and the other unpredictable or unmanageable variations of the components in a brake system. In this paper, effects of chemical components and casting process of gray iron brake disc on its resonant frequency variation have been studied. Especially this paper is focused on the variation in material aspects and manufacturing parameters during disc casting in usual production condition. And their effects are investigated by the variation of out-of-plane modal resonant frequency.
Technical Paper
2009-04-20
Zhongzhe Chi, Yuping He, Greg Naterer
Under intensive braking, such as continuous down-hill braking, high temperatures could be generated in automotive brake disks. The heat dissipation and thermal performance of vented brake discs strongly depends on the aerodynamic characteristics of the air flow through the rotor passages and the geometry configurations of brake discs. In this paper, commercial software GAMBIT is used for geometrical modeling and automatic mesh generating for brake rotors. Then, a computational fluid dynamic package, FLUENT, is employed to simulate the turbulent motions of air flow through the vented discs. Through the numerical simulations, the design criteria regarding the heat transfer rate and air flow rate of the discs are predicted. To optimize the 2-D and 3-D geometrical configurations of the brake discs, commercial software iSIGHT is used to integrate the geometrical modeling with GAMBIT and numerical simulations based on CFD software FLUENT. With the design of experiment studies implemented through this integrated design synthesis process, the thermal performance of brake rotors is greatly improved by optimizing disc outer and inner radii, vane numbers, vane angles, and the radius of vane curvature.
Technical Paper
2008-10-12
G. Barigozzi, A. Perdichizzi, M. Donati
The paper reports on a combined experimental and numerical investigation of the aero-thermal behavior of a vented automotive brake disc. The aim is to assess to which extent nowadays available CFD codes can be confidently used in the automotive brake disc design process. The reference experimental investigation provided the aero-thermal flow characteristics at the exit of a vented brake disc, with a pin type internal geometry and drilling holes. Tests were performed at one disc rotational speed and at several braking conditions. Star CD software was employed to compute the internal flow. Results were compared and discussed in terms of both global and local quantities. A general good agreement between numerical and experimental results was obtained. Thus CFD simulation was proved to be a very useful tool for brake disc designers.
Technical Paper
2008-10-12
Pyung Hwang, Xuan Wu, YoungBae Jeon
During braking, the kinetic energy and potential energies of a moving vehicle are converted into the thermal energy through frictional heat between the brake disc and the pads. Most of thermal energy dissipated through the brake disc. The object of the present study is simulation of heating and cooling processes of brake disc to investigate temperature field and temperature variation during driving along a downhill road. The velocity of automobile is limited by repeated brake when the speed exceeds to the maximum limited. The pad-disc brake assembly is built by 3D model and applied appropriate boundary condition. In the simulation process, the mechanical loads are applied to the thermo-mechanical coupling model in order to simulate the process of heat produced by friction. The Analysis results are compared to the measured data obtained from the downhill road brake experiment. The temperature field distribution in the disc under repeated braking presents a non-uniformity characteristic.
Technical Paper
2008-10-12
Toshikazu Okamura, Hiroyuki Yumoto, Masanori Imasaki
Brake squeal is a critical issue for automotive brake systems and its propensity significantly depends on the natural frequencies of brake discs. The variation in natural frequencies is caused by various factors in the disc manufacturing process, from foundry through machining. To reduce this variation, we analyzed the factorial effects of material and dimensional properties on natural frequencies of brake discs with various configurations by conducting intensive computer-aided engineering experiments. These experiments were performed accurately and quickly with the help of our original brake disc design system. As a result, we determined the critical factors affecting the natural frequencies of brake discs and their contribution.
Technical Paper
2008-10-07
Bruno Ferranti, Aliandro Henrique da Costa Santos, Auteliano Antunes dos Santos Júnior
This study aims to evaluate the heating of brake discs of Formula SAE vehicles, designed by State University of Campinas. The temperature is the most important variable in the dimensioning of the discs. The following steps were performed: definition of the initial boundary conditions and parameters; numerical simulation of the brake disc in a condition characteristic of test benches; validation of the results in a full-scale dynamometer. Supported by the parameters validated, the model was used to simulate the braking along a real race track. The results showed that the temperature is in a safe range.
Technical Paper
2008-04-14
Cristiana Delprete, Carlo Rosso, Roberto Spadotto
In racing design, important and urgent problems have to be solved: on one hand an high level of optimization of shapes and weights is needed for achieving high performance, on the other hand a quick development time is necessary to reduce the time between the new concept and the actual application on racing car as many redesigns are carried out during racing season. In the present paper, a quick design strategy for the brake disc mounting bell is proposed in order to reduce the development time and to reach an high accuracy for improving car performance. The brake disc mounting bell is a poorly studied component, but it has important side effects on the handling and the efficiency of a racing car. The proposed design strategy is developed by means of thermal and static finite element analysis (FEA). The component needs not only a great reduction in weight and rotational inertia but also a great stiffness for obtaining short reaction time in braking system and improving system durability.
Technical Paper
2008-04-14
Edward Palmer, Rakesh Mishra, John Fieldhouse, Jonathan Layfield
Within this paper the convective heat dissipation from the front brake discs fitted to the left and right hand side of a high performance passenger car has been compared. The tools used in this investigation include computational fluid dynamics (CFD) and vehicle testing. The results show that although identical discs are fitted to both sides of the vehicle the disc fitted to the left hand side shows better thermo-aerodynamic properties than that fitted to the right due to the different direction of rotation. The computational model shows strong agreement with the test results; over predicting the average heat transfer coefficient by 4% for the left hand disc and 7.6% for the right disc. The CFD analysis enabled a detailed insight into the air flow and heat transfer distributions that was not possible during the vehicle test regime.
Technical Paper
2007-10-07
Yoshihiro Koyama, Kazuya Okubo, Toru Fujii, Tsuyoshi Nakatsuji
The purpose of this study is to clarify how the residual stress determined by the configuration of weight reduction holes affects the crack initiation in the brake discs for large motorcycles under the over loading condition. Two kinds of test samples of the one-piece type brake disc were used where the configuration of the weight reduction holes were different. The test result showed that the crack initiation life was significantly changed due to the configuration of weight reduction holes. The 3D FEM results of heat transfer and thermal stress analysis explained that the stress relaxation was dependent on the configuration of weight reduction holes of the disc because the initial thermal stress was directly determined by the simple stress distribution around each hole. This study confirmed that the configuration of weight reduction holes plays a decisive role in determining the design of the brake disc.
Technical Paper
2007-10-07
Toshikazu Okamura, Masanori Imasaki
We studied the relationship between disc thickness variation (DTV) and casting material properties and clarified that the circumferential homogeneity of brake discs has significant effects on brake judder. As a solution, we established an integrated system for developing and manufacturing homogeneous brake discs to reduce judder by making the most of our integrated business process from R&D through manufacturing, including our in-house foundries. The system we developed consists of the following elements: foundry engineering to obtain homogeneous discs, an original flake graphite structure index (K-FGI) to measure the homogeneity of our products, and accelerated wear tests on a brake dynamometer to estimate the potential on-brake DTV growth.
Technical Paper
2007-08-05
Pyung Hwang, Xuan Wu, Sang-Woon Cho, Young-Bae Jeon
The ventilated disc brake is divided into a disc with several vents, and the pads with the three dimensional geometry. The frictional heat can cause high temperature during the braking process. The thermal distortion of the brake disc can affect the performance of brake system. The object of present work is determination of temperature distribution and thermal distortion in the disc by two dimensional thermal analysis. During brake, heat flux and convective transfer coefficient are considered as a function of time. The brake disc temperature is found to be satisfactory compared with that of the conventional three dimensional analysis. Thermoelastic deformation of the disc is found from the same axisymmetric finite element model with equivalent mechanical properties. The analysis results are also compared to the measured data in the brake disc thermal experiment.
Technical Paper
2006-11-13
Kiyotaka Obunai, Kazuya Okubo, Toru Fujii, Tsuyoshi Nakatsuji
This study discussed the mechanism of the low speed judder for wave type brake disc developed newly for recent motorcycles. Wavy disc was examined to investigate the effect of wave configurations on the BTV (Brake Torque Variation) behavior. Torque amplitude in braking was compared with respect to the revolution order which represented the multiple number of the number of revolutions. To explain the mechanism at the mode showing largest BTV, the elastic deformation of the pad was analyzed by finite element method concerning geometrical nonlinearity with commercial code. This study found that most crucial BTV appeared on low speed judder was observed at the 3 rd peaks on the revolution order. Test data showed that this crucial BTV was related with the number of waves at the disc periphery, and caused by the indentation of the pad into notched part at disc periphery. Finally, current paper proposed an effective model to predict the amplitude at high order of BTV calculating with the indentation of the pad and the line pressure.
Technical Paper
2006-10-08
Gael Mace, Nicholas Bowler, Geoff Goddard, Denise Morrey
Abstract Cast iron brake discs are commonly used for road and race applications. The graphite flake arrangement of grey cast iron matches the high thermal conductivity requirements of brake discs, although with the brittleness characteristic of this material. Therefore the design of cast iron brake discs is a compromise between a thermally efficient design to reduce the operating temperature and a design generating a controlled tensile stress level to prevent crack failure, with as little mass penalty as possible. The most critical failure mode on competition brake discs is catastrophic crack propagation in the early stages of service life. Dynamometer testing has shown that the initial bedding process greatly reduces the likelihood of catastrophic disc failure. This fact leads to the hypothesis that a heat treatment process occurs on the discs during bedding, increasing their crack resistance. A visual microstructure analysis using conventional and scanning electron microscopy has revealed that the braking face temperature locally exceeds the critical phase transformation temperature during bedding.
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